Method of making curing bags



F. T. HOVEY 2,666,007

METHOD 0F MAM-JG CURING BAGS Filed Jan. 5, 1950 .Pam l2, B954 NIN (ttoruegs Patented Jan. 12, 1954 UNITED- STATES OFF-'ICE'.

METHOD1 0E MAKINGl CURING BAGSl Frank, T.Hovey, Akron, Oliio, assignor. to Tlie Firestone Tire &' Rubber Company, Akron,e Ohio, a corporation of Ohio Application January-3, 1950,. Seriali. No. 136,525

1 Claim.

This inventionL relates, to valved inflatable curingbagsiandgreiers particularly to aiiginert gasses, water andsteam bags ioruse-in; curing-.

or, vulcanizing pneumatic tires-v and. to method of. producing same.

In vulca-nizingpneumatic tires, inflatable formera. commonly referred to as fullfcircle. cur-V ingjbags, arefgenerallyI usedinproviding the requrediinte-rnal pressure to vforce they tire-against the tire mold. V Such curing bags are expansible endless.- tubes composed of rubber, or` rubber-like material; and are provided with metal inflation valve .stems. .to j facilitate.l the introduction ci` air,

waterorothersuitable fluid underpressure. TheY valvefsternsj are secured. to the inner or' base wallsfof;theacuringfbags, extending through said.

WallsI and have means for attachment thereto,

but. considerable difculty.- has been experienced.

ingeiecting.. auid-tightanchorage of the ste.

infor onithe rubber` which, will continuato be fluid tight through, successive tire curing; operations.` In.service,-.after a curing bagy has been usedlin=a;tire curing operation, the. bag is re.

moved from thecuredtireand usedin the cur ing .oi. anotheri tire andinlikemanner for asr many additionaL tire cures` as the conditionof the curing. bag will permit.

andefective tire, it is desirable toget. the maximumnumberoi cures from each bag and to overcome'the causes of bag failures. One of the most commoncauses of failures oi` curing-r bags..

is .leakage ofthe inilationvfluid along` and past the valve stem. Thistype ofbag failure is known asl avalve leak. Twomethods of combatingcuringr bag valve leakshave been` resorted to in; the=art. One method depends upon obtaininga bond between the-rubber and the metalcuring.

bag stem.. and the other methodto mechanically draw the base of a valvestem against the inside. wallet the base portion of the bag thusv obtaining auid tight seal.V Inserting or removing a cur,- ing bag from a.; tire. results in extreme distortion of.` the rubber in the bag walls; however, thev metal valve stems are not distorted which results in-the'rubberprematurely breaking its adhesion or` bond to the metal. Whenl a valve. leak occurs itimay develop during the tireY curingyoperation inzwhich event itis often necessaryA to classify the` tireasdefective. A valve. leak in acuring bag-in which rubber adhesion to the valve' stem isemployed to prevent leaks usua'llyresults` 1n scrapping the bag or atleast-in building into:

thefbageanew' valve stem to replace.l the old.

Building in new-stems. is expensive and noti en Since curing bags are-expensive andA since aleakingY bag may., cause.

it. in?

tirely satisfactory` since bagsv withv replacement or builtf-instemsoftenfailbefore many. addif tionalcures have been obtained. Even so, curing,

forcement at the valve stem so disposed astoV resist tearing of the: rubber adjacent a metal bagrstem.`

Further and. additional objects. and advane tageswill-become apparentduring thev detailed; description which is to follow. Referring tothe..

accompanying drawings:

Figure 1: is a, perspective .view-f of. an. endl por.-

tion of, a ,curingA bag showing. a valve` inpositionv before the bag: is vulcanized;

Figure is a. plan View ofa valve patchas itl appearszwhen blanked out from. asheetlof. rub-A berized, Woven` wire;

Figure is ay sectionalview. through a valve stem and a fragmentary sectionalviewof avalve stem mold showing. assembled rubber. anda valve' stemipatch'as they appear just. before the molding of; the-f rubber and patch. about the valve.

stem;y

Figure- 4 is a .sectional `View. showingthe valve stem, rubber. and patchof Eigure as they appearl after molding;

Eigure is atopplanview of the assembly of:

Figuref. :isV a. fragmentary sectional view of' a.. curingbag embodyingV one formoi the presenti invention; thezstembeing shown partlyv in ele? vationandpartly. in section.

The: invention has. been illustrated in the.

drawingsasapplied to a. curing bag, which may be formed-.oiz butylor naturalrrubb'er compound orof any-.otherfsuitable material, and which is inzthe-formaof a: pliable annular tube in. the. interior-of which-constitutes a; iluid chamber Il into which air, inert gas, steam, water. or the like;` may be introducedgthrough avalve stemindicated generallyv at l2.

togconiormto Lthe size and shapeof. the interior offa.- finished tire; In .service the bag is mounted. inan unvulc-anized tire to providethe internal tirevpressure necessary'l fonproper, molding and" vuicanizing: of tlrief'irev ItV`i has i been found" ad.

visable and ii1;.is-'common'A practice inimostsizes The bag Ht is ofv such. a cross sectional-configuration.when inated asv of bags to form the inner wall or base I3 of the bag thicker than the other wall portions for reasons well known to those familiar with the art.

By reference to Fig. 6 of the drawing, it will be seen that the bag construction comprises two layers I4 and I5 of wire in the general form of the frustum of a hollow cone builtinto the base I3 about but spaced from the stem I2. The wire I6 of these layers may be in the form of Woven wire or the layers may be composed of separate parallel wires held together by a suitable binder. In any event the layers of wirelare embedded in a sheet of rubber preparatory to being incorporated into the structure of the bag. It has been found that a convenient and satisfactory way of rubberizing said wires is by means of a rubber calender by which the layers of wire are'rubbercoated on both sides. If separate wires are to be used, as for example, strands of .025" gage'high carbon wire, such wires are generally simultaneously led from separate spools of a creel through a. rubber calender, in spaced parallel relation, in similar fashion as in the method of rubberizing weftless cord tire fabric. The spacing of the cords is substantial, as for example, if .025" gage wire is used the wires are preferably spaced .1. If Woven wire is used it is rubberized in similar fashion as used in rubberizing square woven fabric for rubber tires.

After the wire has been incorporated into a sheet of rubber, as just described, oval-shaped blanks in the form of valve stem patches I4 and I5 are out therefrom. Blank I5 is somewhat smaller than blank I4 and is laid on I4 so as to provide a stepped-down edge to the assembly of wire layers or blanks, whichassembly may be pressed into conical form if desired. Preferably the wires I6 are separate and parallel in each said layer with the wires 'of blank I4 arranged so as to extend at an angle of approximately 90 to the wires of blank I5. It is to be understood, however, that the invention is not to be limited to two layers of wire since more or but one layer has been found to improve the bag construction.

After the blanks of wires I4 and I5 have been plied up as described, rubber IS is built, in substantially conical shape, in any convenient manner as superimposing a layer ofrubber about a base I9 of the Valve stem I2. Next the wires at the center of the assembled blanks I4 and I5 are spread apart to form a hole through which the end of valve stem I2 opposite base I9 may be passed. The soft unvulcanized rubber permits the wires I6 to be displaced and it hasV been found that such displacement may be conveniently done with an awl commonly used in the rubber industry. The hole is made enough larger than the valve stem so that the edges of the hole may be spaced from the valve stem as will be seen by reference to Figs. 4 and 6. Said assembly of blanks I4 and I5 are pressed against the rubber I8 where it will adhere due to the tacky nature of uncured rubber, although rubber cement may be applied to the surfaces of the blanks or the rubber I8 or both if found desirable to increase the adhesive characteristic of the surfaces or the strength of their union after vulcanization. The said assembled blanks are flexible enough to permit them to be pressed against the rubber I8 after which the assembly of valve I2, rubber I8 and blanks I 4 and I5 are placed ina vulcanizing mold, having bottom and lid 1 and B respectively, and the rubber given only sufficient vulcanization to set the rubber, after which the partially vulcanized valve stem assembly, referred to generally as 4 20, is removed from said mold and incorporated into the base I3 of curing bag I0 before said bag is vulcanized.

To incorporate the assembly into said base the rubber surface of the molded portions, referred to as 9, of assembly 20 is buffed and cemented and the cement permitted to dry, all in accordance with common practice of preparing rubber surfaces for a permanent vulcanized union to another rubber surface. Next the bag base I3 is cut away in form and amounts to approximately the size and shape of valve stem assembly 20. The cut surface of the base may be cemented or otherwise prepared to receive assembly 20 and to permanently unite thereto, by vulcanization, all in accordance with well-known practices in the rubber industry. Next the assembly 20 is placed in position in said base as indicated in Fig. l after which the bag I0 is laid in a curing bag mold and vulcanized, after which a valve washer 2I and nut 22 may be placed on stem I2.

It has been found that the wire reinforcement about the valve stem disposed as described hereinabove is very effective in preventing air, steam, water or other fluid inflation pressure medium from leaking between the valve stem andthe rubber, and also prevents the rubber of the base I3 from breaking open near the said stern. This latter fault is a serious problem in curing cord tires and the present invention has been found to have outstanding merit in preventing bag failures from bag bases cracking open or breaking through near the valve stems. Whatever the true explanation may be for the better results obtained from the construction described, it is though that it is due, at least in part, to the following factors:v 1. The layers of wire are suiciently flexible to,

avoid a region of abrupt change from fiexing or distortion of the rubber at the valve stern but rigid enough to resist flexing to a degree that gradually dissipates such distortion.

2. The wire in the reinforcing layers I4 and I5 will not permit air or other internal inflation medium to flow therethrough as in the case of textile cords, thus if a rupture develops from the inside of a curing bag and extends to the wire layers its progress is interrupted and said air or other medium will not leak through the wire.

3. The woven wire or spaced parallel wires I3 provide openings therebetween so that rivet-like rubber extends through layers i4 and I5 and closely surrounds each wire thereby providing an improved union between said wire layers and the rubber body of the curing bag.

4. Heretofore it has been common to reinforce curing bags about the valve stems with textile fabric which were subject to deteriorationy by the high repeated vulcanizing heat. No such deterioration develops to an objectionable'degree in the wire of the present invention.

While, throughout the specification, reference has been made to a valve and a valve stem, it

will be understood that these are shop terms used' details of construction and arrangement of parts, and the right is herein reserved to invoke such changes as fall within the scope of the appended claim Without departing from the spirit of the invention.

What is claimed is:

The method of making a full-circle tire curing bag having a base portion and a metal valve stem which stem includes a barrel and base portion comprising applying uncured rubber compound to said valve stem base and about said barrel adjacent the valve stem base in substantially conical form with the base of said coneshaped rubber adjacent said stem base, incorporating a layer of Wires having openings therethrough into a sheet of uncured rubber, cutting a patch from the combined sheet of rubber and layer of wires, forming a hole in the center of said patch adapted to receive said barrel, attaching said patch free of tension to substantially conical surface of the rubber applied to said valve stem and molding and partially vulcanizing said rubber forming a valve stem head, forming a valve stem opening through said bag base, incorporating said valve stem head in said bag base in said opening and molding and vulcanizing the aforementioned elements into a composite Whole.

FRANK. T. HOVEY.

References Cited in the le of this patent UNITED STATES PATENTS Number Name Date 1,270,345 TeW June 25, 1918 1,435,970 Merrill Nov. 21, 1922 1,910,128 Seniler May 23, 1933 2,218,639 Crowley Oct. 22, 1940 2,308,268 Corson Jan. 12, 1943 2,318,376 Crowley May 4, 1943 2,476,817 Charnes July 19, 1949 2,564,662

Baker Aug. 21, 1951 

